1. Field of the Invention
The present invention relates to a printing mechanism and a thermal printer.
2. Description of the Related Art
A thermal printer has been known as a printer configured to perform printing on a recording paper (heat-sensitive paper). A printing mechanism mounted to the thermal printer includes a head mechanism having a thermal head, and a platen mechanism having a platen roller configured to feed the recording paper. According to this configuration, the platen roller is rotated under a state in which the recording paper is nipped between the thermal head and the platen roller, to thereby convey the recording paper. When the recording paper passes through the thermal head, the thermal head is appropriately heated so that printing is performed on the recording paper.
Further, the printing mechanism includes a cutter mechanism configured to cut the recording paper having passed through the thermal head. The cutter mechanism includes, for example, a fixed blade incorporated in the head mechanism and a movable blade incorporated in the platen mechanism. According to this configuration, the movable blade is slid with respect to the fixed blade so that the recording paper is nipped and cut between the movable blade and the fixed blade. A position of the movable blade is detected, for example, by an optical sensor.
Incidentally, as the recording paper used in the above-mentioned thermal printer, a roll sheet wound around a core tube or the like is often used. Thus, the recording paper is conveyed under a state in which the recording paper has a curling with a predetermined curvature conforming to a winding direction of the roll sheet.
In this case, when the recording paper having been cut by the cutter mechanism remains in the vicinity of the delivery slot of the thermal printer without being taken, an upstream edge portion of the recording paper in a paper path direction may enter upstream of the cutter mechanism in the paper path direction due to the curling or the like. In this state, when the recording paper to be printed next is subjected to a cutting operation by the cutter mechanism, the upstream edge portion of the recording paper having been printed previously is cut together with the recording paper to be printed next. Then, the upstream edge portion of the recording paper having been printed previously is cut into a slender paper piece, and the slender paper piece may remain in the printing mechanism.
Here, between the movable blade and a frame for supporting the movable blade, a clearance is formed so that the movable blade can slide smoothly. In this case, when the above-mentioned paper piece or other foreign matters (hereinafter collectively referred to as “paper piece or the like”) enter, for example, the clearance between the movable blade and the frame, the above-mentioned optical sensor may be covered with the paper piece or the like, or light projected from the optical sensor may be unintentionally blocked. Consequently, erroneous operation of the movable blade or the like may be caused. Therefore, there is still room for improvement in view of improving reliability.
Under the above-mentioned circumstances, in this technical field, there have been demanded a printing mechanism and a thermal printer, which prevent entry of the paper piece or the like between the platen frame and the movable blade and are highly reliable.